As Persad sees it, dilemmas in medical ethics and health policy often involve two questions. One is a factual or descriptive question concerning “which benefits an intervention will have.” (183) The other is an ethical question concerning “how to distribute those benefits.” (183) Persad provides the following example to tease out the distinction:

determining who should receive priority for scarce vaccines in a pandemic involves answering two questions: the descriptive (factual) question of which benefits these vaccines are expected to have for their recipients and the normative (value) question of how those prospective benefits should be distributed. (183)

Persad is interested in considering how fair procedures can be used to address questions of the first sort—the “epistemological and factual questions in medicine.” (183) He sets for himself the following task: to “consider how fair procedures have been and can be used to develop and weigh factual evidence in medicine.” (184) Persad foresees an increase in both the significance and frequency of “debates over the validity and weight of medical evidence” as the amount of medical evidence that is both required and amassed increases. He foresees an acceleration in this trend, which he credits to

the expansion of clinical data collection and analysis; the growing relevance of scientific evidence to medical practice…; and the use of evidence to support payment and insurance coverage decisions that have financial implications for patients and providers. (184)